Is it standard to say that an evaluation function estimates the “goodness” of a position?
Yes, "goodness" is a common description of the value generated by an evaluation function.
For example,
"Artificial Intelligence" p. 77;
"Knowledge-Free and Learning-Based Methods in Intelligent Game Playing" p. 15;
"Tenth Scandinavian Conference on Artificial Intelligence" p. 125; and
"Algorithms and Networking for Computer Games" p. 80.

The "position" is to the complete state of the game at some instant. A single position includes the locations of every piece on a game board at that instant, and also includes a few other bits of information -- who's turn it is; whether castling is still a legal option; etc.

I suspect that "the position" is a synecdoche, referring to the total state by a small part, the physical location (physical position) of some piece on the game board, based on earlier usage in military tactics of "positioning" troops relative to natural cover or relative to enemy troops.